1. Field of the Invention
The present invention relates to a golf ball, more particularly to improving durability of the golf ball.
2. Description of the Related Art
A golf ball is required to have durability since it is repeatedly hit. As a material constituting a cover of a golf ball, ionomer resins are known. Since a golf ball having an ionomer resin cover is relatively rigid, it is excellent in resilience, durability, and workability. However, it has a problem of poor shot feeling and controllability.
Therefore, Japanese patent publications Nos. H01-308577, H05-277208, H07-132152 and H08-182777 and PCT International Application Japanese Translation No. H11-500776, for example, propose an improvement of shot feeling and controllability of an ionomer resin cover. Japanese patent publication No. H01-308577, for example, discloses a technology of blending a rigid ionomer resin and a flexible ionomer resin. Japanese patent publication No. H05-277208 discloses a technology using two or more ionomer resins having a relatively low modulus value. Japanese patent publication No. H07-132152 discloses a use of a heated mixture of an ionomer resin; a ternary copolymer resin consisting of α-olefin, an unsaturated carboxylic acid ester and an unsaturated carboxylic acid; and a glycidyl group-containing α-olefin copolymerized resin as a base resin of a cover. Japanese patent publication No. H08-182777 discloses a heated mixture of three kinds consisting of an ionomer resin, an anhydrous maleic acid modified olefin copolymer and a glycidyl group modified styrene base block copolymer with JIS-A hardness of 30 to 90 as a base resin of a cover. PCT International Application Japanese Translation No. H11-500776 discloses a process for producing a golf ball cover composition, which process comprises: a) forming a polymer comprising a first monomeric component comprising an olefinic monomer having from 2 to 8 carbon atoms; a second monomeric component comprising an unsaturated carboxylic acid based acrylate class ester having from 4 to 22 carbon atoms; and an optional third monomeric component comprising at least one monomer selected from the group consisting of carbon monoxide, sulfur dioxide, an anhydride monomer, an unsaturated monocarboxylic acid, an olefin having from 2 to 8 carbon atoms, and a vinyl ester or vinyl ether of an alkyl acid having from 4 to 21 carbon atoms; and saponifying the polymer with an inorganic metal base to obtain a polymer salt having a saponification degree of about 1 to 50%.
In recent years, a use of a biodegradable resin as a polymer material has been under study from a viewpoint of environmental conservation. For example, each of Japanese patent publication No. 2006-247224 and US Patent publication No. 2004/0209701 discloses a golf ball using a biodegradable resin.